docs: def _concatenate_file(self, file_list, output):
          '''
          Call unix "cat" to concatenate a list of files
  
          Parameters
          ----------
          file_list: list
              List of strings, each leading to a file. These files are the ones to
              be concatenate together. E.g.:
                  ["/path/to/file1", "/path/to/file2"]
          output: str
              Path to file to which to the files in file_list will be concatenated
              into.
  
          '''
          to_cat = ' '.join(file_list)
          logging.debug("Concatenating files: %s" % (to_cat))
          cmd = "cat %s > %s" % (to_cat, output)
          extern.run(cmd)